Coupling controller

ABSTRACT

Covers equipment employing a sensor, such as a magnetic pickup, which senses the speed of the output shaft of a fluid drive apparatus, and determines whether the output shaft speed differs from a predetermined reference speed. If there is a difference or error, a correction signal is generated for correspondingly controlling the fluid drive apparatus to reduce the error signal, step by step, to a substantially zero magnitude. The correction signal, derived from the magnetic pickup which is spaced from but coupled to a gear device on the output shaft, is converted into a series of variable width pulses which are employed for the control function.

United States Patent 5.11. 53 (W.E.R.) (inquired), 12; 91/361, 362, 364,366, (step-by-step); 192/033; 103/35; 415/16, 30; 417/22, 42; 60/(G)(Digest 2 91/429 Processor Primary Examiner- Edgar W. GeogheganAttorneys-Jefferson Ehrlich, Tennes l. Erstad and Robert G.

Crooks ABSTRACT: Covers equipment employing a sensor, such as a magneticpickup, which senses the speed of the output shaft of a fluid driveapparatus, and determines whether the output shaft speed differs from apredetermined reference speed. If there is a difference or error, acorrection signal is generated for correspondingly controlling the fluiddrive apparatus to reduce the error signal, step by step, to asubstantially zero magnitude. The correction signal, derived from themagnetic pickup which is spaced from but coupled to a gear device on theoutput shaft, is converted into a series of variable width pulses whichare employed for the control function.

Signal Conditioner Pickup lo Transducer II B Looo Loud IO may be a motoror pump or conveyor belt or other controlled device.

Patented March 30, 1971 3,572,959

6 Sheets-Sheet 1 Fig. i.

Signal Processor Conditioner Motor l5 Operator Prime Mover Load PickupTransducer Gear Device INVENTOR. William J. Shoughnessy MW MC4 ATTORNEYPatented Malrch so, 155

6 Sheets-s 3 INVENTOR. WIIIIOITI J Shauqhnessy ATTORNEY w 5 8;; hal o?:252:

Nmm 2 o I; O nnm Patented March 30, 1971 6 Sheets-Sheet 5 A3 mmm.noWmnm. H

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INVENTOR.

William J. Shoughnessy ATTORNEY Patented March 30, 1971 6 Sheets-Sheet 4NEW .3. a; 9% m2. mnovw. mmo uh m2 m8 m8 m8 M M 0 V 3a 2E 501R ATTORNEYPatented March 30,1971 3,512,959

6 Sheets-Sheet 5 R24 %R23 R8 R28 CR3 84 Fig. 70.

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INVENTOR. William J. Shuughnessy BYMMW M ATTORNEY Patented March 30,1971 6 Sheets-Sheet 6 mum mum

m0 mum wmo INVENTOR. William J. Shuuqhnessy BM ATTORNEY CQUPMNGCUNTROLLER This invention generally relates to a method and apparatus offeedback control wherein the variable parameter of an apparatus orprocess, called the controlled variable, is main tainted at or near apredetermined or preset value, this predetermined or preset value beinghereinafter sometimes called the set point. This is accomplished bymeasuring the value of the controlled variable and comparing this valuewith the set point value, then generating a signal proportional to thedifference between the two values, and using the difference signal tomodify some phase of operation of the apparatus or process so that thevalue of the controlled variable will be returned very closely to theset point value.

In particular, this invention relates to a control system employing atranslating device, hereinafter called the processor, which compares asignal corresponding to a controlled variable of the system with thesignal corresponding to the set point and operates on the differencebetween these two signals or values, this difference being the errorsignal. The control system operates in such a way as to modify somephase of the process or apparatus so that the difference between thesignal corresponding to the value of the controlled variable and thesignal corresponding to the set point value, that is, the error signal,will actuate apparatus to reduce the error signal to near zero.

More particularly, this invention relates to a speed control systememploying a processor as described above which is used in conjunctionwith a reversible motor operator as, for example, the type 904F motoroperator manufactured by the HONEYWELL Corporation. The motor operatorfurnishes the mechanical power to modify a significant phase of theprocess or apparatus in question in order to obtain the desired controlof the speed. In addition to the above, the processor employs atranslating device to which is applied a first signal corresponding tothe value of the controlled variable and another signal corresponding tothe value of the set point, both signals being supplied as inputs to thetranslating device. The motor operator is, in turn, controlled by theoutput of the translating device. The processor operates on the inputsignals so that, when a significant difference or error signal exists,the motor operator is caused to operate in such a way that it will, stepby step, cause some phase of the process to be modified so that thedifference or error signal is reduced substantially to zero.

This invention may be employed, for'exarnple, in connection with anywell-known fluid drive of the variable speed type which is typicallyused as a coupler or transmission medium between a fixed speed rotatingpower source, such as an induction motor, and a rotating shaft-poweredload which is to be driven at variable speeds or slowly accelerated ordecelerated to a fixed or predetermined speed. One form of such a, fluiddrive is commercially available as the V82 Gyro! Fluid Drive. in such amechanism power transmission in the fluid drive is achieved through avariable coupling between the driving member, sometimes called theimpeller, and a driven member, sometimes called a runner. By regulatingthe quantity of fluid inserted in to the rotating vortex of the fluiddrive which couples the impeller with the runner, the output shaft speedcan be varied over a wide range. The quantity of fluid in the couplingvortex may be controlled by adjusting the position of an openended scooptube located within the vortax of the fluid drive. The fluid, which maybe continuously fed to the vortex chamber by a pump coupled to the inputshaft, is returned to the reservoir of the fluid drive through the scooptube. The relative position of the end of the scoop tube within thevortex determines the steady state level of fluid in the couplingapparatus and thus determines the amount of energy transferred to theoutput shaft.

This invention will be better understood from the more detaileddescription and explanation hereinafter following when read inconnection with the accompanying drawing in which:

FIG. ll illustrates a schematic diagram of the main components of thespeed control system that may be employed in practicing the invention;

H6. 2 shows a form of pick up or transducer arrangement that may beemployed in this invention to obtain pulses so as to sense the speed ofthe output shaft of the fluid-coupling apparatus;

PKG. 3 illustrates a conditioning arrangement for averaging the pulsesobtained by the pickup or transducer arrangement and producing anequivalent voltage;

FIG. d shows a group of pulses developed by the apparatus of thisinvention;

H6. 5 shows a processing arrangement responsive to the current developedby the conditioning arrangement of Fit 3 for producing correspondinggroups of pulses;

FIG. 6 shows the equipment which is coupled to the processingarrangement of HO. 5 to control the operation of an actuator;

FIG. 7 shows a monostable vibrator which is embodied in the conditioningcircuit of N6. 3; and

FIG. 8 shows a push-pull integrator circuit which is another part of theconditioning circuit of FIG. 3.

FIG. 1 schematically depicts one application of the invention in which arotating shaft-powered mechanical load 10, as, for example, a conveyorbelt, is to be driven at a constant speed, the value of which may beselected at will be an operator. The equipment involves a prime mover l,for example, an electric motor or gasoline engine operating at a nearlyconstant speed, which is coupled, through a coupler 2, to the inputshaft 3 of the inter coupling transmission element or fluid drive 4. Theoutput shaft 5 of this transmission element 4 which may be, for example,a fluid drive product manufactured by the assignee of this applicationand known as a Gyrol Fluid Drive, or that apparatus shown and describedin the R. M. Nelden U.S. Pat. No. 3,096,620, issued Jul. 9, 1963,entitled Fluid Drive Improvement, assigned to the same assignee, may beset at or below the speed of the input shaft 3 by manipulating theposition of a control rod 7, sometimes called the scoop tube, of thefluid drive machine 4, as will be explained. The speed of the outputshaft 5 is a function of load 10 as well as of the position of the scooptube 7' of element 4. if the load 10 on the output shaft increases, theoutput shaft speed will decrease. Similarly, if the load on the outputshaft 5 decreases, the shaft speed will increase but never to a valuegreater than, for example, about 97 percent of the input shaft speed. Byrepositioning the scoop tube 7 in the coupling vortex of the fluid drivemachine 6} following a load change, the output shaft speed can bemaintained at a nearly constant value thereby to maintain the speed atsubstantially constant value.

A feedback control system which automatically regulates the speed of theoutput shaft 5 is one of the key components of this invention. Theoutput shaft speed is measured by a suitable transducer ll which iscoupled to a gear or gearlilre disc 12, as shown inl IG. 2. Theelectrical signal supplied by the transducer ll, which corresponds tothe shaft speed is fed to a signal conditioner 13.

in this particular embodiment for illustration, the transducer may be amagnetic pickup, such as an ELECTED model 3030-AN, and it is located inclose proximity to the gear or gearlike disc 12 which is mounted on theoutput shaft 5 of the fluid drive transmission equipment i. Thiscombination of the transducer ii and the gear device l2! provides ameans for sensing the output shaft speed. The transducer ill by beingcoupled to gear device l2, supplies a series of pulses, the frequency orrepetition rate of which is directly proportional to the output shaftspeed. The pulses are fed to the signal conditioner 13 which convertsthe pulses picked up by transducer ll into a substantially continuousvoltage (or current). The change in the magnitude of the continuousvoltage is directly and linearly proportional to the frequency orrepetition rate of the incoming pulses due to the teeth of the geardevice ill...

A schematic circuit of the signal conditioner circuit employed to obtainthe continuous voltage just referred to for use in the speed controlsystem embodiment of this invention is shown in H6. 3. The speed of theoutput shaft 5 of FlG. l is measured as a pulse rate frequency by theelectromagnetic pickup 11. which is generally shown in FIGS. 1 and 2.The sensing tip 20 of the electromagnetic pickup 11 is physically spacedwith respect to the outer diameter of the gear or sprocket wheel 12,which is mounted on the output shaft 5, as shown in FIG. 2. As each ofthe gear teeth passes the tip 20 of the pickup 11, the change inmagnetic field of the pickup device 11 induces a voltage in a coil (notshown) contained within the body of the pickup device 11. Thus, a gear12 with 48 teeth will produce a train of pulses at a frequencyfwhereandfis measured in cycles per second and n speed of shaft in r.p.m.

The signal conditioner equipment of FIG. 3 accepts the pulses from themagnetic pickup 11 in conductors 30 and 31 and produces a DC outputvoltage signal which is directly and linearly proportional to thefrequency of the incoming pulses as already mentioned. Thisfrequency-to-voltage conversion is realized by generating a pulse ofprecise amplitude and time duration for each of the irregularly shapedpulses generated by the magnetic pickup 11 and then measuring theaverage DC value of such pulses over any given period of time.

The general technique of measuring the average DC value of the pulses isillustrated in FIG. 4. Pulses are generated within the signalconditioner of FIG. 3 each of which has an amplitude uch as E and a timeduration such as T as shown in FIG. 4. The average value of thisperiodic waveform is ET T But the time interval of the pulse, which iscaused by one tooth of the gear device 12, is T=l /f. Therefore, theaverage value of the waveform shown in FIG. 4 is V,,,.,.=Eft,.

As will be explained, pulses of the precise time duration shown in FIG.4 are produced by a monostable multivibrator circuit incorporated in thesignal conditioner of FIG. 3. The incoming pulses from pickup 11 areapplied through conduc tors 30, 31 to the base and the grounded emitterof transistor Q3. As soon as the incoming pulse signal from the pickupdevice 11 goes positive, transistor O3 is driven into saturation andremains in that state until the incoming pulse signal level from pickupdevice 11 falls below zero. A square wave is thus produced at thecollector of transistor Q3. The negative going edge of the square waveis transformed into a negative pulse by capacitor C2 and resistor R12 ofFIG. 3. The negative pulse is applied to the base of transistor Q4producing a positive pulse at the collector of transistor Q4. Thispositive pulse then is applied to the base of transistor Q5 through R13,thereby triggering the monostable multivibrator of FIG. 3.

The multivibrator portion of the signal conditioner of FIG. 3 has beenredrawn in FIG. 7 for greater clarity. The multivibrator circuitoperates, in response to the positive pulse from the collector oftransistor O4, to produce at the collector of transistor Q5 a negativerectangular pulse having a time duration proportional to the product ofthe capacitance of capacitor C4 and the resistances of resistor R27 andthat portion of resistor R28 not bypassed by its wiper, said capacitorand resistors being connected to the collector of transistor Q5 as shownin FIGS. 3 and 7. The negative rectangular pulse is shown in FIG. 7a.Potentiometer R28 is adjustable so as to set the multivibrator pulseperiod which controls the basic sensitivity of the signal conditioner ofFIG. 3 in volts per cycle.

The multivibrator pulses produced at the controller of transistor Q5,which are shown in FIG. 70, as already noted, are inverted by transistorQ6 and then applied to a push-pull driver circuit employing PNPtransistor Q7 and NPN transistor Q9. This push-pull driver circuit ofFIG. 3 has been redrawn in FIG. 8 for greater clarity. The output of thepushpull driver circuit is applied to an integrating circuit comprisedof resistor R29 and capacitor C5. Wit no input pulse signal applied toline 30, 31 extending to the signal conditioner, that is, at zero speedof the output shaft 5, transistors ave Q6 and Q7 are continuouslysaturated. The voltage on capacitor C5 under this condition is nearlyequal to the DC voltage B20. When a pulse signal derived from themagnetic pickup 11 is present, however, a train of positive pulses ofprecise width T, (see FIG 7a) and having a magnitude of about B20 voltswill traverse resistor R14 and will appear at the collector oftransistor Q6. For the duration of each of these pulses, transistor Q9will be in saturation and capacitor C5 will therefore discharge throughthe collector-emitter circuit of transistor Q9 toward ground potential.The resultant average voltage on capacitor C5 may be obtained from theexpression:

The voltage on capacitor C5 is applied to a series pair ofemitter-followers Q10 and Q11 shown in FIGS. 3 and 8. The NPN-PNPemitter-follower combination of transistors Q10 and Q11 reduces theoffset to near zero because the baseemitter voltage drops of the twotransistors Q10 and Q11 are in series opposition. This series oppositionconnection also reduces the temperature sensitivity of the circuit. Theoutput signal from the emitter of transistor Q11 is directly connectedby conductor to the base of transistor O9 in the processor of FIG. 5.

The continuous output signal from the signal conditioner 13 (see FIG. 1)is applied to the processor circuit 14 which, as already noted, isanother important part of the invention and will be described inconnection with FIG. 5. Included in the signal conditioner of FIG. 3 isthe set point adjustment resistor R5. As already noted, this set pointadjustment determines the reference voltage level which is to becompared with the input signal. The difference between the referencevoltage level and the input signal is called the error signal as alreadyindicated above.

In response to a continuous error signal, the processor 14 (see FIG. 1)controls the conduction duty cycle of two solid state AC switches, i.e.,thyristor switches Q21 and Q25 of FIG. 5, to be subsequently describedwith reference to FIG. 5, and these switches may be included as part ofthe processor 14. The AC switches (Q21 and Q25) are connected to each ofthe two control windings of a different type of motor operator MA (whichis designated 16 in FIG. 1). This motor operator, for example, may be aHONEYWELL model 904F Modutrol unit. Depending upon the polarity of theerror signal or signal pulses, one or the other of the two AC switchesQ21 or Q25 will be selectively pulsed. The ratio of the ON time (whenthe selected switch is conducting) to the total ON plus OFF time isdirectly related to the magnitude of the error signal. The crank arm 15of the motor operator 16 (see FIG. 1) moves during the time that theselected AC switch in the processor is ON or conducting. The directionof motion of the crank arm 15 depends on which of the two AC switches(Q21 or Q25) in the processor is conducting. Both switches cannotconduct simultaneously. The crank arm 15 of the motor operator 4 isconnected to the scoop tube 7, as shown in FIG. 1, so that the scooptube 7 is moved in discrete increments becoming smaller as the errormagnitude is reduced. Because of the slow response of the fluid drive ofthe motor operator 4, these discrete steps are actually translated intoa relatively smooth transition in speed of the output shaft 5 of FIG. 1.

The mode of control, in which the final control element (i.e. motoroperator 4) is pulsed step by step rather than driven continuously, maybe called time proportional control. This mode of control is especiallysuited to apparatus and processes characterized by a dead time and aslow rate of response. The scoop tube 7 of the fluid drive, rather thanbeing continuously moved at a fixed rate when an error signal ispresent, is moved in incremental steps. The effect is that the controlaction stops and waits for the slowly responding process to catch up.This results in a control system which is quite accurate and dynamicallystable without overshooting and without excessive slowness in respondingto an error signal and which is also free from offset. This inventionachieves these goals through an electronic circuit which is novel indesign and low in cost.

The schematic circuit for the time-proportional control processor 1.4 ofH0. 1 (or controller) is shown some detail in F16. 5. Three capacitors,C28, C23 and C3i charging at the same time, each from a separate currentsource. Capacitor C2? is charged with the collector current oftransistor Q29 which receives current from source B23 of Fl -G. 3;capacitor C2? is charged with the collector current of transistor Q33which receives current from source B28; and capacitor C31 is chargedwith the collector current of transistor Q32 which receives current fromsource 1331. Transistor Q23 is turned off during the charging period.

If the voltage from the emitter of transistor Q11 of FIG. 3 (whichcorresponds to the voltage from the signal conditioner 13 of FIG. 1)applied to the base of transistor Q29 substantially equals the referencevoltage applied through conductor 161i (see N6. 3) to the base oftransistor Q33, that is, if the error voltage is zero, the collectorcurrents of transistor Q29 and transistor 031) will be substantiallyequal. Capacitors C23 and C29 of FIG. 5 will then charge at about thesame rate. The biasing potentiometers R20 and R21 are adjusted suchthat, under this condition, the voltage on capacitor C31 will reach thefiring level of unijunction transistor Q23 before the voltage on eithercapacitor C23 or capacitor C29 reaches the tiring level of the siliconunilateral switches (SUS) Q26 or Q27 to which they are respectivelyconnected. When the unijunction transistor Q23 fires, however, currentis injected into the base of transistor Q28 through resistor R31,rendering transistor Q23 conductive. Transistor Q23 is thus turned on sothat both capacitors C28 and are rapidly discharged through thecollector-emitter circuit of transistor Q28. When the emitter current ofunijunction transistor Q23 decays sufficiently, this transistor Q23 willturn off and capacitors C28, C29 and C31 will one again begin charging.This cycle will repeat continuously.

The cycle time or repetition rate is regulated by adjustment ofpotentiometer that} which controls the amplitude of all three chargingcurrents. Potentiometer R41 is included to allow introduction of adeadband into the control circuit so that, if desired, no correctiveaction will take place until the error signal exceeds some presetamplitude.

if a sufficient voltage difference appears across the bases oftransistor Q29 and transistor 030, the differential amplifier action oftransistor Q29 and transistor Q31) will result in a current unbalance inthe collectors of these transistors. 1f the voltage on the base oftransistor Q29, for example, falls below that on the base of transistorQ30, as would be the case if the speed of the output shaft 5 (seeFIG. 1) dropped below the set point, the collector current in transistorQ29 would increase while the collector current in transistor Q30 woulddecrease by the same amount. if the difference is great enough, thevoltage on capacitor C28 would reach the firing level of transistor Q26before the voltage on capacitor C31 would reach the firing level ofunijunction transistor Q23. When transistor Q26 fires, rectifier SCR1will be turned on,-allowing current to flow through resistor R21 andinto the gate of thyristor Q21. Thyristor Q21 is a solid-state AC switchconnected between one of the two coils of the motor operator MA, thefinal control element, and the common terminal of both coils of deviceMA. As long as thyristor Q21 remains turned on, the motor operator MAwill be driven in a counterclockwise direction.

Thyristor Q21 will remain turned on until capacitor C31 reaches thefiring level of transistor Q23. When unijunction transistor Q23 fires,it promptly removes whatever charge remains on capacitor C23 andcapacitor C29 as described earlier, and also turns on transistors Q23and Q24. When transistor Q23 and transistor Q24 are turned on, theanodes of devices SCRl and SCRZ are etfectiveiy grounded so thatwhichever of the two may have been conducting will be turned off. inthis example, device SCRl and, consequently, transistor Q21 will both beturned off. The greater the unbalance in the collector currents oftransistor Q29 and transistor Q30, the earlier will transistor Q26 tireand thyristor Q21 will be turned on and the greater will be the dutycycle.

The embodiment of the controller circuit for actuating the motoroperator 16 of F161. 1 is shown in H6. s and is intended to supplementthe circuit of HQ. 5' and its description. The controller includes threecapacitor-charging circuits, each having a level-sensitive triggeringdevice which operates either on a thyristor network or a reset network.The capacitorcharging circuit formed by resistor R415, resistor RVl andcapacitor 34 determines the cycle period, T. This section of thecontroller derives its operating voltage from capacitor C31. When thevoltage across capacitor C3 3 reaches the firing level of unijunctiontransistor 037, a pulse is transmitted to the base of transistors Q38,Q39 and Q40 through resistors R40, R41 and R42. Thus, the threetransistors are momentari- 1y driven into saturation. When transistorQ39 saturates, any charge accumulated on either capacitor C32 orcapacitor C33 is removed, reducing the voltage on both capacitors to alevel near zero. Transistors Q38 and Q46) divert current from the anodesof switching transistors Q33 and Q35, causing these two devices to beturned off if either of them had been previously turned on. Thus,thyristors Q33 and Q36 will also be turned off if either had beenpreviously turned on.

After the reset pulse from Q37 decays (a few milliseconds), capacitorsC32 and C33 will begin to charge because of current flow from thecollectors of transistors Q31 and Q32. if the potentiometric transducerRT is in such a position that the voltage from terminals A to B remainsnearly zero throughout the AC voltage cycle, then capacitors C33 and C32will charge at nearly equal rates. The circuit components are selectedso that, under this condition, the unijunction transistor Q37 will fire,discharging capacitors C32 and C33, before the voltage level on eithercapacitor C32 or capacitor C33 builds up to a level sufficient tobreakdown device D6 or device D9 which may be silicon unilateralswitches.

As the wiper of the potentiometric transducer RT of the motor operatormoves a sufficient amount from the position at which the currents fromthe collector of transistor Q31 and Q32 are nearly equal, the currentsflowing from the collectors of transistors Q31 and Q32 will becomeincreasingly unequal or unbalanced. if the wiper moves to the left,current from the collector of transistor Q32 will increase while currentfrom the collector of transistor Q31 will decrease; if the wiper movesto the right current from die collector of transistor Q31 will increasewhile current from the collector of transistor Q32 will decrease.

Note that in all cases, current flows from the collectors of transistorsQ31 and Q32 only when the voltage at the upper terminal (as shown in theFIG.) of the transformer secondary is positive with respect to the lowerterminal.

As collector current of either transistor 031 or transistor Q32increases, the rate at which charge is accumulated on the associatedcapacitor (C32 or C33) will increase until finally the voltage oncapacitor C32 or C33 reaches the triggering level of device 1336 ordevice D33 respectively before the voltage on capacitor C34 reaches thetriggering level of transistor Q37.

When, for example, the motion of the wiper is to the right, the voltageon capacitor C32 will eventually reach the triggering level of deviceD36 before the voltage on capacitor C34 reaches the triggering level oftransistor Q37. When this level is reached, device D36 breaks down,transmitting a positive current pulse to the gate of SCR device 03d.Device 034 will then turn on and remain turned on because of acontinuous flow of current from anode to cathode through resistor R47and the gate-anode terminals of thyristor Q33. The continuous currentflow through the gate-anode terminals of the bidirectional thyristor Q33will maintain a low-impedance conduction path from anode 1 to anode 2 ofthat device. The resulting flow of current through the energizedactuator coil will cause the actuator to move continuously in onedirection. Devices Q34 and Q33 will continue to remain turned on onlyuntil unijunction transistor Q37 tires, at which time transistor Q38saturates, interrupting the flow of current through device Q34. Device@3 3 will then turn off and remain turned T absence of current flow intothe gate of thyristor device Q33 will cause that device to be turned offwithin a n cycle.

if the motion of the wiper were to the left, cc D9 would have fired,initiating the same sequence of events just described but with respectto devices Q35, Q36 and Q40 rather than devices Q33, Q34 and Motion ofthe actuator would then have been in the reverse direction.

The greater the departure of the wiper of R from the balance position,the greater will be the unbalance of the collector currents oftransistors Q31 and Q32 and the earlier in the cycle will occur thetriggering of devices us and i 39. Thus, the duty cycle, i.e., thepercentage of each cycle the; the actuator is in motion, will increaseas the amount of departure of the potentiometer wiper from position atbalance.

it is apparent, then, that by proper phasing of the response of theactuator with transducer motion, a closed loop control system can beefiected.

Because of the nature of the circuit formed by transistors QBll, Q32,resistors R31, R32 and R33, the increase in current flow into eithercapacitor C32 or capacitor C33 in response to maximum potentiometerwiper travel will not exceed more than about 1.6 times the value atbalance. This limits the maximum duty cycle to about 50 percent.

Thus, the invention provides an arrangement for controlling a couplerl-which may be a fluid drive couplerinterposed between a source of powerand a loadto be driven by the power source. The control arrangementembodies a feedback system, as is plainly shown in HQ. l. The feedbacksystem is in the form of a loop interconnecting or coupling the outputshaft with the coupler mechanism 4. "if he transducer 11 senses andmonitors the output shaft 5 and generates a series of pulses the numberof which is proportional to the speed of shaft 5, i.e. the operatingproperty or parameter of the load. These pulses are converted byequipment 13 to a continuous voltage, for example, which is proportionalto the received sensing pulses. The so-called processor 14 compares thecontinuous voltage produced by equipment l3 with a datum or referencesignal in the form of another voltage which corresponds to thepredetermined setting for the coupler d. The difference between the twovoltages-sometimes called the error signal-generates another series ofpulses in the processor M which are poled and employed for controlling,step by step, the operation of themotor operator lb. The control of thecoupler 4 is performed in discrete steps or increments in order to movea mechanical element, coupled to the motor operator 16, the mechanicalelement being a scoop tube in the fluid drive 4. The scoop tube 7controls the vortex flow of the drive 4 to return the output shaft 5 toits speed at the set point, i.e., the predetermined speed, withoutoverreacting to or overshooting shaft speed changes. The movement of thescoop tube is accomplished by the modutrol unit 16 (MA) which is, ineffect, the final control element. The steps become smaller and smalleruntil the set point is reached.

Although this invention has been shown and described as applicable tothe control of the speed of any form of load, such as a conveyor system,the invention will be equally applicable to the control of the pressureof fluid delivered by a variable speed pump, such as a centrifugal pump.The pressure control system of this invention may be used, for example,in applications where the pump discharge pressure is the desiredcontrolled variable. ln systems of this type, the output shaft 5 of thefluid drive 4 may be coupled, by any well-known means, to a centrifugalpump which may be considered as the load it). It is the object of thepressure control system to maintain the pump discharge pressuresubstantially constant by automatically adjusting the pump shaft speedin accordance with the varying pressure of the fluid system. if the pumpdischarge pressure were, for example, to drop because of a demand for anincreased flow rate in the fluid system supplied by the pump, thepressure control system should respond by withdrawing the fluid drivescoop tube 7 until the operating speed of the pump, which is coupled tothe output shaft d of the fluid drive 4, increases to a rate sufficientto maintain the desired pump pressure substantially constant. This couldbe readily accomplished by replacing the gear mechanism 12 and thetransducer 11 by any well-known pressure sensor responsive to changes inthe fluid pressure under control and having the pressure sensor, inturn, control an appropriate signal conditioner. This will control theprocessor 14 so as to'control, step by step, the equipment leading tothe scoop tube 7. These These variants would be apparent to thoseskilled in the art who are familiar with this invention.

While this invention has been shown and described in certain particularembodiments for explanation and illustration, it will be apparent thatthe invention may be embodied in many other widely varied organizationswithout deprecating from the spirit and scope of the inventive conceptsset forth in this disclosure.

lclaim:

1. Control apparatus for a fluid drive coupled to a load, comprisingmeans for changing the coupling of the fluid drive step by step as themagnitude of the load changes from a predetermined value to return theload to said predetermined value said means comprising means coupled tosaid fluid drive and responsive to changes in the magnitude of the loadto produce pulses of a magnitude corresponding to the changes in theload magnitude for maintaining substantially constant the power suppliedthrough the fluid drive to the load.

2. Control apparatus for a fluid drive coupled to a load, comprisingmeans for changing the coupling of the fluid drive step by step as themagnitude of Cue load changes from a predetermined value to return theload to said predetermined value, said means comprising anelectromagnetic structure having a controlled moving element-whichchanges the rotating vortex of the fluid drive step by step to changethe power delivered to the load.

3. Control apparatus for a fluid drive coupled to a load according toclaim 2, in which the coupling changing means generates pulses of amagnitude and polarity which are responsive to load changes, and meansresponsive to said pulses to vary the rotating vortex of the'iluid drivestep by step.

4. Control apparatus for a moving load comprising a fluid drive coupledto the load by a shaft, means responsive to the speed of the shaft togenerate a first plurality of pulses, means responsive to said firstplurality of pulses to produce a second plurality of pulsescorresponding to changes required to return the power developed by theload to a predetermined value, and means responsive to the secondplurality of pulses to change the rotating vortex of the fluid drivestep by step.

5. Control apparatus for a moving load according to claim 4 in which themeans for generating the first plurality of pulses comprises a toothedgear and a coil coupled to said gear, the magnetic field of whichchanges as the rate at which the teeth of the gear move past said coil.

6. Control apparatus for a moving load according to claim 4 in which themeans responsive to the second plurality of pulses comprises anelectromagnetic structure having an armature which moves in onedirection to change the rotating vortex in one direction and which movesin the opposite direction to change the rotating vortex in the oppositedirection.

7. Apparatus for controlling a power-supplied load comprising a drivecoupled between the power source and the load, sensing means forproducing a first plurality of pulses corresponding to changes in theoperating property of the load, means for converting said firstplurality of pulses to a continuous voltage representation of saidpulses, means responsive to the difi'erence between the continuousvoltage and a predetermined magnitude to produce a second plurality ofpulses which are poled to correspond to the directional change to bemade in the operating property of the load, and means responsive to saidsecond plurality of pulses to directionally change the operatingproperty of the load.

8. Apparatus for controlling a power-supplied load according to claim 7in which the sensing means comprises a rotating mechanical gear coupledto the load and a magnetic detector adjacent to the teeth of the gear togenerate pulses as the gear rotates.

9. Apparatus for controlling a power-supplied load according to claim 7in which the means responsive to the second plurality of pulses is anelectromagnetic structure having a controlled moving element whichchanges the coupling of the drive.

10. Apparatus for controlling a load comprising a fluid drive which iscoupled to the load by a rotatable shaft, a gear mounted on said shaft,a coil juxtaposed to said gear and producing a first group of pulsescorresponding to the changes in the speed of said gear, means forintegrating said first group of pulses into a continuous voltage, acomparator for comparing said continuous voltage with a predeterminedvoltage, means responsive to the departure of the continuous voltagefrom the predetermined voltage to generate a second plurality of pulses,and an electromagnetic structure having a moving element to change therotating vortex of the fluid drive according to said second plurality ofpulses.

11. Apparatus for controlling a load according to claim 10, in whichsaid predetermined voltage is adjustable to correspond to thepredetermined operating property of said load.

12. Apparatus for controlling a load according to claim 10, in which themoving element of the electromagnetic structure is operated step by stepto correspondingly change the rotating-vortex of the fluid drive.

13. Apparatus for controlling a load according to claim 12, in which themoving element of the electromagnetic structure is mechanically coupledto a device for physically changing the rotating vortex of the fluiddrive.

14. Apparatus for controlling the changing operating property of a load,comprising a fluid drive coupled to the load by a rotatable shaft, meansresponsive to changes in the speed of said shaft to produce a continuousvoltage corresponding to said changes in said speed, means responsive tosaid continuous voltage to generate pulsations of a magnitude andpolarity corresponding to the departure of the operating property ofsaid load from a predetermined value, and means responsive to saidpulsations to change the rotating vortex of said drive step by step toreturn said operating property of said load to said predetermined value.

15. Apparatus for controlling the changing operating property of a loadaccording to claim 14 in which the means to change the rotating vortexincludes an electromechanical element coupled to a device for physicallychanging the rotating vortex of the fluid drive.

16. Apparatus for controlling a variable pressure load comprising afluid drive which is coupled to said load by a rotatable shaft,pressure-sensitive means electrically coupled to said fluid drive andsaid load and producing pulses responding to changes in the pressure ofsaid load, and means responsive to the departure of the pressure sensedby said pressure sensitive means from a predetermined value to changethe pressure of said load to return it substantially to itspredetermined value.

17. Apparatus for controlling a variable pressure load according toclaim to in which the variable pressure load includes a pump.

18. Apparatus for controlling a fluid-conveying device comprising afluid drive which is coupled to said fluid conveying device,pressure-sensitive means electrically interposed between said fluiddrive and said load and producing pulses responding to the pressure ofthe fluid conveyed by said device, and means responsive to the departureof the pressure of the conveyed fluid from a predetermined value forelectrically controlling the fluid drive so as to return the pressure ofthe fluid conveyed by said device substantially to its predeterminedvalue.

19. Apparatus for controlling a fluid conveying device according toclaim 18 in which the fluid drive is controlled step by step to returnthe pressure of the fluid conveyed by the fluid device substantially toits predetermined value.

1. Control apparatus for a fluid drive coupled to a load, comprisingmeans for changing the coupling of the fluid drive step by step as themagnitude of the load changes from a predetermined value to return theload to said predetermined value said means comprising means coupled tosaid fluid drive and responsive to changes in the magnitude of the loadto produce pulses of a magnitude corresponding to the changes in theload magnitude for maintaining substantially constant the power suppliedthrough the fluid drive to the load.
 2. Control apparatus for a fluiddrive coupled to a load, comprising means for changing the coupling ofthe fluid drive step by step as the magnitude of the load changes from apredetermined value to return the load to said predetermined value, saidmeans comprising an electromagnetic structure having a controlled movingelement which changes the rotating vortex of the fluid drive step bystep to change the power delivered to the load.
 3. Control apparatus fora fluid drive coupled to a load according to claim 2, in which thecoupling changing means generates pulses of a magnitude and polaritywhich are responsive to load changes, and means responsive to saidpulses to vary the rotating vortex of the fluid drive step by step. 4.Control apparatus for a moving load comprising a fluid drive coupled tothe load by a shaft, means responsive to the speed of the shaft togenerate a first plurality of pulses, means responsive to said firstplurality of pulses to produce a second plurality of pulsescorresponding to changes required to return the power developed by theload to a predetermined value, and means responsive to the secondplurality of pulses to change the rotating vortex of the fluid drivestep by step.
 5. Control apparatus for a moving load according to claim4 in which the means for generating the first plurality of pulsescomprises a toothed gear and a coil coupled to said gear, the magneticfield of which changes as the rate at which the teeth of the gear movepast said coil.
 6. Control apparatus for a moving load according toclaim 4 in which the means responsive to the second plurality of pulsescomprises an electromagnetic structure having an armature which moves inone direction to change the rotating vortex in one direction and whichmoves in the opposite direction to change the rotating vortex in theopposite direction.
 7. Apparatus for controlling a power-supplied loadcomprising a drive coupled between the power source and the load,sensing means for producing a first plurality of pulses corresponding tochanges in the operating property of the load, means for converting saidfirst plurality of pulses to a continuous voltage representation of saidpulses, means responsive to the difference between the continuousvoltage and a predetermined magnitude to produce a second plurality ofpulses which are poled to correspond to the directional change to bemade in the operating property of the load, and means responsive to saidsecond plurality of pulses to directionally change the operatingproperty of the load.
 8. Apparatus for controlling a power-supplied loadaccording to claIm 7 in which the sensing means comprises a rotatingmechanical gear coupled to the load and a magnetic detector adjacent tothe teeth of the gear to generate pulses as the gear rotates. 9.Apparatus for controlling a power-supplied load according to claim 7 inwhich the means responsive to the second plurality of pulses is anelectromagnetic structure having a controlled moving element whichchanges the coupling of the drive.
 10. Apparatus for controlling a loadcomprising a fluid drive which is coupled to the load by a rotatableshaft, a gear mounted on said shaft, a coil juxtaposed to said gear andproducing a first group of pulses corresponding to the changes in thespeed of said gear, means for integrating said first group of pulsesinto a continuous voltage, a comparator for comparing said continuousvoltage with a predetermined voltage, means responsive to the departureof the continuous voltage from the predetermined voltage to generate asecond plurality of pulses, and an electromagnetic structure having amoving element to change the rotating vortex of the fluid driveaccording to said second plurality of pulses.
 11. Apparatus forcontrolling a load according to claim 10, in which said predeterminedvoltage is adjustable to correspond to the predetermined operatingproperty of said load.
 12. Apparatus for controlling a load according toclaim 10, in which the moving element of the electromagnetic structureis operated step by step to correspondingly change the rotating vortexof the fluid drive.
 13. Apparatus for controlling a load according toclaim 12, in which the moving element of the electromagnetic structureis mechanically coupled to a device for physically changing the rotatingvortex of the fluid drive.
 14. Apparatus for controlling the changingoperating property of a load, comprising a fluid drive coupled to theload by a rotatable shaft, means responsive to changes in the speed ofsaid shaft to produce a continuous voltage corresponding to said changesin said speed, means responsive to said continuous voltage to generatepulsations of a magnitude and polarity corresponding to the departure ofthe operating property of said load from a predetermined value, andmeans responsive to said pulsations to change the rotating vortex ofsaid drive step by step to return said operating property of said loadto said predetermined value.
 15. Apparatus for controlling the changingoperating property of a load according to claim 14 in which the means tochange the rotating vortex includes an electromechanical element coupledto a device for physically changing the rotating vortex of the fluiddrive.
 16. Apparatus for controlling a variable pressure load comprisinga fluid drive which is coupled to said load by a rotatable shaft,pressure-sensitive means electrically coupled to said fluid drive andsaid load and producing pulses responding to changes in the pressure ofsaid load, and means responsive to the departure of the pressure sensedby said pressure sensitive means from a predetermined value to changethe pressure of said load to return it substantially to itspredetermined value.
 17. Apparatus for controlling a variable pressureload according to claim 16 in which the variable pressure load includesa pump.
 18. Apparatus for controlling a fluid-conveying devicecomprising a fluid drive which is coupled to said fluid conveyingdevice, pressure-sensitive means electrically interposed between saidfluid drive and said load and producing pulses responding to thepressure of the fluid conveyed by said device, and means responsive tothe departure of the pressure of the conveyed fluid from a predeterminedvalue for electrically controlling the fluid drive so as to return thepressure of the fluid conveyed by said device substantially to itspredetermined value.
 19. Apparatus for controlling a fluid conveyingdevice according to claim 18 in which the fluid drive is controlled stepby step to return the pressure of the fluid conveyed by the fLuid devicesubstantially to its predetermined value.